Hydraulic fracturing uses large amounts of pressurized water — mixed with sand and chemicals — to crack subterranean rocks and release oil or natural gas. Up to 10 million gallons of water can go into a single well.

The study, released today by the nonprofit group Ceres, examined 25,450 fracked wells across the United States and found that 47 percent lie in areas that face high or extremely high “water stress.” In those areas, at least 80 percent of the available fresh water is already being used in homes, farms or businesses.